There are two standard wide screen aspect ratios in current use in commercial motion picture theater exhibition. One format is the Wide Screen Academy Format which was adopted in the 1950's, which is sometimes referred to as the "Flat" format (because it uses a spherical lens without a cylindrical anamorphic lens). The projected area in the Flat format has an aspect ratio of 1.85:1, and accounts for about 70% of all commercial theater projection. Present original cameras (in-the-field and studio cameras) that photograph in the Flat format, take camera film frames that each have a height of slightly less than 4 perforations and that have an aspect ratio of about 1.33:1. The entire area of each film frame can be used in television broadcast, which currently uses an aspect ratio of 1.33:1. For motion picture theater projection, only about 60% of the height of each film frame is projected, to produce an aspect ratio of 1.85:1 on a theater screen.
In the practice of the system called Cinemascope, or Scope (aspect ratio of 2.35:1), the original camera uses a high quality anamorphic lens which produces a camera film image that is horizontally compressed by 50%. Almost the same camera film frame size (4 perforations high and same width) is used as when photographing in the Flat format, except that in the Scope format the aspect ratio of the photographed image, or original scene, is reduced by half from 2.35:1 to 1.175:1. Release Scope prints are made, whose film frames are identical to those of the original (but edited) camera frames. In a theater, an anamorphic projection lens is used to project the images of the Scope frames onto a theater screen. The projection lens produces a horizontal expansion of 100%, so the projected image has an aspect ratio of 2.35:1, even though the film frame image has an aspect ratio of only 1.175:1. The Scope process has the advantage that substantially the entire height of the camera-photographed film frames are used (instead of only about 60% as for the 1.85:1 aspect ratio of the projected area in the Flat format) so the Scope process can potentially produce a satisfactory image across a larger projection screen width. A limiting factor in the use of the Scope process is that an expensive anamorphic projection lens would be required to produce a good projected Scope image. Lenses are subject to large amounts of astigmatism, linear image distortion, chromatic aberration, and other aberrations. The aberrations are potentially very large where an anamorphic lens must produce a large horizontal or vertical compression or expansion. In order to obtain a high quality projected image of a prior Scope film, an expensive anamorphic projection lens would be required. In practice, anamorphic lenses of moderate cost (e.g. $1800) are used, which produce a wide image of only moderate quality. In addition, if a theater is to project Scope images (0.700 inch high) as well as Flat images (0.446 inch high), a separate primary lens is required for each (each primary projection lens costs about $1200). The Scope format has been limited to about 30% of theatrical projection.